Jtag interface

28 Apr 2010


Is it possible (without too much microsurgery) to attach a JTAG debugger to the MBED? I would be thinking of the Keil Ulink specifically.

Also, will you be publishing full schematics and code for the 'interface' chip...which I assume is some sort of FPGA?

Another item on the wish list...separate start-up and init code (source) modules that can be user-configured, rather than having the processor start up in one mode and then revert through user code. One of the main reasons for wanting this is that I fully intend to outrageously abuse the chip with a hot-air gun, to see if I can use it at cake-cooking temperatures. It would be nice to know that I have full control over the start-up operating conditions when I do it.

Many thanks, and thanks for a great eval system...


28 Apr 2010

1. The chip is exposed on top, you should be able to solder thin wires to the leads if you so desire. I'm not sure if it will work, since the interface chip also uses the JTAG connection (for flashing and semihosting).
2. The interface chip is another LPC (an ARM7 I think). There were some noises from mbed guys about full schematics, but I really doubt you'll see the source of the internal firmware, especially since even the interface libraries are still closed source. (There's also a strong hint in the fact that firmware updates are encrypted...)
3. You can compile any code you want with an offline compiler, just target it for an LPC1768. With the online compiler, you can probably override Reset_Handler, but don't expect any of the library code to work then.

28 Apr 2010


I'd guess that they use the JTAG from the other chip to load code into the running LPC1768.  Their schematics aren't too clear on where Reset and and the JTAGs are coming from\going to, but they are labeled as though they are being used.


16 Aug 2011

I created a Notebook page with a recipe http://mbed.org/users/iva2k/notebook/jtag/